Nondipper hypertension is associated with increased cardiovascular morbidity and mortality. Vitamin D deficiency is associated with cardiovascular diseases such as coronary artery disease, heart failure, and hypertension. Vitamin D deficiency activates the renin-angiotensin-aldosterone system, which affects the cardiovascular system. For this reason, a relationship between vitamin D deficiency and nondipper hypertension could be suggested. In this study, we compared 25-OH vitamin D levels between dipper and nondipper hypertensive patients. The study included 80 hypertensive patients and they were divided into two groups: 50 dipper patients (29 male, mean age 51.5 ± 8 years) and 30 nondipper patients (17 male, mean age 50.6 ± 5.4 years). All the patients were subjected to transthoracic echocardiography and ambulatory 24-hour blood pressure monitoring. In addition to routine tests, 25-OH vitamin D and parathormone (PTH) levels were analyzed. All the patients received antihypertensive drug therapy for at least 3 months prior to the evaluations. 25-OH vitamin D and PTH levels were compared between the two groups. No statistically significant difference was found between the two groups in terms of basic characteristics. The average PTH level of hypertensive dipper patients was lower than that of nondipper patients (65.3 ± 14.2 vs. 96.9 ± 30.8 pg/mL, P < .001). The average 25-OH vitamin D level of hypertensive dipper patients was higher than that of nondipper patients (21.9 ± 7.4 vs. 12.8 ± 5.9 ng/mL, P = .001). The left ventricular mass and left ventricular mass index were lower in the dipper patients than in the nondipper patients (186.5 ± 62.1 vs. 246.3 ± 85.3 g, P = .022; and 111.6 ± 21.2 vs.147 ± 25.7 g/m(2), P < .001, respectively). Other conventional echocardiographic parameters were similar between the two groups. Daytime systolic and diastolic blood pressure measurements were similar between dippers and nondippers, but there was a significant difference between the two groups with regard to nighttime measurements (nighttime systolic 118.5 ± 5.8 vs.130.2 ± 9.6 mm Hg, P < .001; and nighttime diastolic 69.3 ± 4.8 vs.78.1 ± 7.2 mm Hg, P < .001, respectively). Our results suggest that vitamin D deficiency has a positive correlation with blood pressure and vitamin D deficiency could be related to nondipper hypertension. The measurement of vitamin D may be used to indicate increased risk of hypertension-related adverse cardiovascular events.